Implemented Eclipse MicroProfile Health Check not updating all of the returned Values

Question

I am running a Java (zulu-openjdk:17.0.8.1) application with Payara (5.2022.5).

The application has a health check endpoint that calculates the current heap usage. It is set up according to the Eclipse MicroProfile Health Check API documentation (https://github.com/eclipse/microprofile-health/blob/main/README.adoc). Besides the status it returns some of the calculated values as well. I noticed that the values are not all updated as I would expect.

The heapUsage value is not updated after the first call to the endpoint.

{"status":"UP","checks":[{"name":"heap-usage","status":"UP","data":{"usedMemory":"4275572456","totalMemory":"6062866432","heapUsage":"0.04","threshold":"0.90",
"maxMemory":"10001317888"}}]}

{"status":"UP","checks":[{"name":"heap-usage","status":"UP","data":{"usedMemory":"3726759584","totalMemory":"5837422592","heapUsage":"0.04","threshold":"0.90",
"maxMemory":"10001317888"}}]}

Code Example:

public class HealthChecks {

  @Produces
  @Liveness
  HealthCheck checkHeapUsage() {

    return () -> HealthCheckResponse
        .named("heap-usage")
        .status(getHeapUsage() <= 0.9)
        .withData("heapUsage", formatDecimal(getHeapUsage()))
        .withData("threshold", formatDecimal(0.9))
        .withData("usedMemory", getUsedMemory())
        .withData("maxMemory", getMaxMemory())
        .withData("totalMemory", getTotalMemory())
        .build();
  }

  private String formatDecimal(double usage) {
    NumberFormat format = new DecimalFormat("#0.00");
    return format.format(usage);
  }

  private double getHeapUsage() {
    return Long.valueOf(getUsedMemory()).doubleValue() / getMaxMemory();
  }

  private long getUsedMemory() {
    return getTotalMemory() - Runtime.getRuntime().freeMemory();
  }

  private long getMaxMemory() {
    return Runtime.getRuntime().maxMemory();
  }

  private long getTotalMemory() {
    return Runtime.getRuntime().totalMemory();
  }
}

I suspected the formatDecimal method could be the issue and cast the value to a long instead. With this change none of the values are updated anymore.

{"status":"UP","checks":[{"name":"heap-usage","status":"UP","data":{"usedMemory":"4275572456","totalMemory":"6062866432","heapUsage":"0.04","threshold":"0.90",
"maxMemory":"10001317888"}}]}

{"status":"UP","checks":[{"name":"heap-usage","status":"UP","data":{"usedMemory":"4275572456","totalMemory":"6062866432","heapUsage":"0.04","threshold":"0.90",
"maxMemory":"10001317888"}}]}

Code Example:

  @Produces
  @Liveness
  HealthCheck checkHeapUsage() {

    return () -> HealthCheckResponse
        .named("heap-usage")
        .status(getHeapUsage() <= 0.9)
        .withData("heapUsage", (long) getHeapUsage())
        .withData("threshold", formatDecimal(0.9))
        .withData("usedMemory", getUsedMemory())
        .withData("maxMemory", getMaxMemory())
        .withData("totalMemory", getTotalMemory())
        .build();
  }

Can somebody please provide insights why this is the case and how to get new values when calling the endpoint.

Thanks very much!